1. Chemistry Laboratory, Department of Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
2. University Institute of Technology, University of Ngaoundere, Ngaoundere, Cameroon
3. Department of Chemistry, University of Buea, Faculty of Sciences, Buea, Cameroon
4. School of Chemical Engineering and Mineral Industries, University of Ngaoundere, Ngaoundere, Cameroon
5. Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Bielefeld, Germany